I work in health care also and you DEFINITELY do not want to skimp when it comes to your feet. Around me the most common options are runners shoes (I personally wouldn't recommend these as the mesh they are made of isn't going to be very water proof), Danskos, Birkenstocks, and Crocs (they may be the ugliest shoe ever made, but apparently they are VERY comfortable). I personally have a pair of Redwing clogs that I frequently rotate the insoles out of. For insoles I've been getting by with OTC Dr. Scholls, but I've been wanting to get a fitting for something even more specific to my feet.
My biggest secret though is getting good SOCKS. I found a nice deal on some Under Armor runners socks with built in padding at Nordstrom Rack and have been working on wearing them out. You want something with extra padding and probably something either made of synthetic fabrics or wool. Both will be better at wicking away moisture from your feet and won't compress throughout the day like cotton. Really, cotton is just the worst thing you could buy for socks.
Finally, while it may not be much of an issue for a nurse doing clinicals, but if you are going to be standing, but standing still, for long periods you can look into compression stockings. These will keep the blood from pooling in your lower legs which will end up hurting after a while. There are commercial products out there, but to get the really good ones you'll need a prescription to get fitted, but you'll also be around a lot of doctors, so maybe get one to do you a favor (there's nothing unethical or unprofessional about asking them, these aren't a medication we're talking about).
I know what forum we are on here, but my last piece of advice is to pay whatever it takes. If you are comparing two pairs of shoes and one fits you like a dream and another fits you "well enough" but is cheaper, don't try and save some money here, go for the best option.